湘鄂地区钻探效果分析及勘探方向

Drilling exploration result analysis and exploration direction in the border areas of Hunan and Hubei provinces.

湘鄂地区属中扬子区，有４套烃源层（上震旦统，下寒武统，奥陶系，下志留统）、４套储集层（上震旦统，下寒武统，中、上寒武统，下奥陶统）和２套良好的区域盖层（志留系和下寒武统），可划分为２套成油气系统（第一套以下寒武统为盖层，完整有效，是最首要的勘探层系；第二套以志留系为盖层，保存条件优劣不均，也是重点勘探层系）。该区已勘探３０余年，但勘探一直未获大的突破，统计钻入下古生界和震旦系的３２口井油气显示情况，结果表明：油气勘探未获突破的重要原因是很多探井钻遇地层生储盖组合不全。认为该区至少存在２类勘探领域：①海相内幕圈闭，是最现实的勘探领域，利川复向斜、花果坪复向斜和桑植—石门复向斜是有利区带；②推覆带下盘圈闭，有利勘探区带主要分布在桑植—石门复向斜之内。要获得湘鄂地区海相地层的勘探突破，关键是要选择古今封盖条件均好的圈闭钻探。图２表４（王孝陵摘）

Bordary areas between Hunan and Hubei provinces belong to Zhongyangzi area, there are 4 sets of source rocks (i.e. Upper Sinian, Lower Cambrian, Ordovician and Lower Silurian), 4 sets of reservoir rocks (i.e. Upper Sinian, Lower Cambrian, Middle/Upper Cambrian and Lower Ordovician) and 2 sets of good regional seals (i.e. Silurian and Lower Cambrian) in the areas, dividing them into 2 petroleum forming systems. The first is the most important exploration target, its seal is Lower Cambrian, being complete and efficient. The second also is major exploration target, its seal is Silurian, its preservation conditions vary widely. Oil and gas exploration has been carried out for more than 30 years in the areas, but no important discoveries are obtained. The statistics of hydrocarbon shows from 32 wells that penetrated Lower Paleozoic and Sinian show that the main reason why important discoveries for oil and gas exploration cannot be obtained is because of uncompleted assemblage of sources, reservoirs and seals of the strata penetrated by many exploration wells. Based on analyses of large quantity of geological data, this paper demonstrates that there are 2 kinds of exploration fields in the areas, namely inside traps of marine formations, they are the most practical exploration fields, favorable regions for finding the traps are Lichuan synclinorium, Huaguoping synclinorium, Sangzhi Shimen synclinorium; traps within footwall of nappe structure belt, favorable regions for seeking out the traps distributing mainly within Sangzhi Shimen synclinorium. The key that important discoveries for oil and gas exploration can be obtained in the marine sedimentary cover of the areas is the selection of the traps with good seal condition to drill. Subject